add R.apply

I'm surprised this function isn't yet defined. It's similar to [clojure.core/apply][1], the difference being that Clojure's apply is variadic whereas Ramda's is a curried binary function.


[1]: http://clojuredocs.org/clojure.core/apply

Is this the desired `@sig`? Is `*...` how we represent zero or more arguments of any combination of types?